The findings of a new study warns that combining the antibiotics Vancocin and Zosyn may cause children to face an increased risk of acute kidney injury.

Researchers with The Children’s Hospital of Philadelphia published a study earlier this month in the medical journal JAMA Pediatrics, indicating that a combination of the two antibiotics more than tripled the risk of acute kidney injury.

Vancocin (vancomycin) and Zosyn (piperacillin sodium/tazobactam sodium) are often administered together for the treatment of serious infections in children.

The researchers conducted a retrospective cohort study, looking at data on nearly 2,000 children who were hospitalized for three or more days and who received vancomycin intravenously, in addition to one other antipseudomonal β-lactam combination therapy. The data was taken from six large children’s hospitals from January 1, 2007 through December 31, 2012.

According to the findings, 157 of those children developed acute kidney injury (AKI). That represented 8.2% of the children involved in the study overall, but when researchers looked at children who were specifically given Vancocin concomitantly with Zosyn, the percentage jumped to 11.7%. The researchers determined that the combination of the two drugs was associated with increasing odds of acute kidney injury for each day the child was hospitalized, at more than three times the risk of other combinations including Vancocin.

“Coadministration of IV vancomycin and piperacillin/tazobactam may increase the risk of AKI in hospitalized children,” the researchers concluded. “Pediatricians must be cognizant of the potential added risk of this combination therapy when making empirical antibiotic choices.”

Acute kidney injuries involve sudden kidney failures or kidney damage that occurs over the course of a few hours or days. They can cause confusion, nausea, fatigue, tiredness, a lack of urine, swelling in the legs, ankles and around the eyes, and in severe cases can cause coma or seizures. In serious cases, dialysis may also be needed until the kidneys recover.

Risks increase with every previous kidney injury, and recurring acute kidney injuries can ultimately result in chronic kidney disease or renal failure.